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Why Stages?

Developing, integrating, testing, running and maintaining large client/server applications typically involve diverse setups. Stages are Riena´s approach to deal with that. Stages are a concept - not a service or a set of classes.

All the different setups of servers and clients are almost identical (and that´s what they should). However, there is a small amount of - ermm - stuff (!) that is different. Basically, this mostly boils down to strings that are different e.g. within URLs (e.g. remote service locations) or other data that gets configured with extensions.

That looks cool. Suppose we could just write that once and use it within different environment setups aka stages.

StringVariableManager come to the rescue

Fortunately there is this great StringVariableManager within the bundle 'org.eclipse.core.variables'. One of things it can do is substituting variable expressions within strings with their definition, e.g.

"This is a ${what} bundle." would become "This is a great bundle." with the definition: what := "great"

The StringVariableManager can be configured programmatically via its API but more useful in our case by extensions, i.e. we can define variables e.g. with such an expression

<extensionpoint="org.eclipse.core.variables.valueVariables"><variabledescription="Name of the host to connect to"name="service_host"readOnly="true"initialValue="http://localhost:8080"/></extension>

With that we got all for plumbing the pieces together. What is missing is a nice artifact from the Eclipse/OSGi ecosystem to package our stages.

Stage fragments

Why not putting all those stage dependent stuff into fragments? Fragments are lightweight and a perfect place for data. One stage - one fragment. As mentioned at the beginning there might be various stages (client/development, client/test, client/production, ..). And of course this pattern can also be applied to the server environment setups.

Fragments need a host bundle that defines the context for the fragment. Typically there is a bundle that plays the role of a main bundle, e.g. within Riena´s sample client application it is the "org.eclipse.riena.sample.app.client" bundle. This main bundle can be used as the host bundle for the stage fragments.
For convenience we store the stage fragments within a special folder in the main bundle. Within our sample application client you can find a folder called "stagefragments" that contains the stages (currently just one!).

Depending on the required stage the appropriate stage fragment needs to be activated, e.g. added to your launch configuration.